Yu-Cheng poisoning

The adverse human impacts of PCBs have been investigated in occupationally exposed workers as well as individuals poisoned with PCB-contaminated rice oil in Japan and Taiwan (Yusho and Yu-Cheng poisonings).91,107-109 In addition, recent studies have shown a correlation with in utero exposure to PCBs and subtle neurodevelopmental and neurobehavioural deficits in children.110 These effects were observed in children with relatively low-level environmental exposure to PCBs and thus have raised concerns regarding the potential adverse effects of low level in utero exposure to organochlorine compounds during critical periods of foetal development. 

PCDFs are very similar to dioxins and, like them, are very toxic, especially 2,4,7,8-tetrachlorodibenzofuran, although this is not quite as toxic as TCDD. They have been found to be contaminants of PCBs and in the Yusho and Yu-Cheng poisoning incidents were more abundant in the PCBs than was usual. As with dioxins and PCBs, there are many different isomers and congeners. 

Evaluation of Human Studies. Limited information on immunological effects of PCBs in humans is available from studies of people exposed in the workplace, by consumption of contaminated fish and other marine foods, by consumption of contaminated rice oil in the Yusho and Yu-Cheng poisoning incidents, and via general enviromnental exposures. A comparison of PCB levels in blood and breast milk in some of these studies is included in Appendix A. 

Children born to mothers from the Yu-Cheng poisoning episode had higher prevalence of bronchitis or pneumonia at 6 months of age, respiratory tract infections at 6 years of age, and middle ear infections at... 

Omission of Relevant Studies on PCBs. Several panelists noted that the current version of the toxicological profile does not include recently published studies on PCBs, as well as some older references. Section 3 of this report identifies specific cases where relevant references were apparently missing or not cited. Responding to this comment, representatives from ATSDR noted that studies published in 1999 and in the last half of 1998 obviously could not be included in the draft profile, since it was published in December, 1998 however, some panelists noted that selected earlier studies were not referenced. The panelists debated whether the profile should include more information on the Yusho and Yu-Cheng poisoning incidents, as Section 3.2.1 of this report describes in greater detail. 

Yusho and Yu-Cheng Incidents. Several panelists recommended that ATSDR consider including more information on the Yusho and Yu-Cheng poisoning incidents from Japan and Taiwan, respectively, in the Toxicological Profile for PCBs. These incidents involved two populations that consumed rice oil contaminated with complex mixtures of chemicals, which included furans, PCBs, and other compounds. Analyses of these incidents are documented in... 

Estimates of the dosage of toxic compounds received by victims of the Yusho and Yu-Cheng poisonings are dependent upon the chemical specificity of the analytical methods used. There is no doubt that the PCB involved had undergone partial oxidation and consequently, the overall toxicity of the fluid was the combined effect of compounds of concern. 

Ryan JJ, Levesque D, Panopio LG, etal. 1993a. Elimination of polychlorinated dibenzofiirans (PCDFs) and polychlorinated biphenyls (PCBs) from human blood in the Yusho and Yu-Cheng rice oil poisonings. Arch Environ Contain Toxicol 24 504-512. 

The carcinogenic effects of PCDDs and PCDFs have been extensively investigated in several highly exposed groups, including industrial workers, herbicide applicators, individuals poisoned in the Yusho and Yu-Cheng incidents in Japan... 

Appendix A. Related information is also available from the Yu-Cheng accidental poisoning incident in Taiwan (Chen et al. 1992,1994 Guo et al. 1995 Lai et al. 1994). Data from adults exposed to PCBs are available from studies by Schantz et al. (1996a, 1996b, 1999) and from evaluations of victims from the Taiwan poisoning episode (Chen et al. 1985 Chia and Chu 1984,1985). 

Human poisonings from consumption of PCB mixtures include the well-known Yusho rice oil poisoning in Japan (1968), where PCB fluids became mixed inadvertently with rice oil used for cooking. The actual level of contamination of the rice oil was low, about 0.2%. About 2000 people were poisoned in 1978 in a similar incident in Yu-Cheng, Taiwan. The principal symptoms in both cases were related to headache. Adipose tissue from Yusho patients was found to contain up to 75 ppm of PCBs. Cancer development was not statistically connected with people poisoning by PCBs. Later investigations have shown that the toxicity of these PCB-contaminated rice oils was probably not primarily due to the PCBs themselves, but to the traces of polychlorinated dibenzofurans (PCDFs), which they contained. We will consider the formation of furans and dioxins in the following section. 

A poisoning very similar to the Japanese Yusho incident occurred in Taiwan in 1978-1979 and is known as the Yu-Cheng incident. In this... 

Mass poisoning of more than 2000 people by contaminated rice oil (Yu-cheng disease, Taiwan) federal law banned US production of PCBs... 

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